Two-stage overhead process condenser for distilling columns



June 27, 1967 K. WARTENBERG TWO-STAGE OVERHEAD PROCESS CONDENSER FOR DISTILLING COLUM NS Filed Aug. 25, 1964 4 Sheets-Sheet l June 27, 1967 K. WARTENBERG 3,328,264

TWO-STAGE OVERHEAD PROCESS CONDENSER FOR DISTILLING COLUMNS Filed Aug. 25, 1964 4 Sheets-Sheet 2 June 27, 1967 WARTENBERG 3,328,264

TWO-STAGE OVERHEAD PROCESS CONDENSER FOR DISTILLING COLUMNS Filed Aug. 25, 1964 4 Sheets$heet 3 I June 27, 1967 K. WARTENBERG TWO-STAGE OVERHEAD PROCESS CONDENSER FOR DISTILLING COLUMNS 4 Sheets-Sheet 4 Filed Aug. 25, 1964 United States Patent 3,328,264 TWO-STAGE OVERHEAD PROCESS CONDENSER FOR DISTILLING COLUMNS Kurt Wartenberg, 14 Kemmansweg, Kettwig (Ruhr), Germany Filed Aug. 25, 1964, Ser. No. 391,844 Claims priority, application Austria, Sept. 19, 1963, A 7,526/63 It) (Ilaims. (Cl. 202-189) This invention relates to condensers that are used as part of a processing system. More specifically, the present invention is concerned with a two-stage surface condenser which employs air-cooling for condensing and cooling the overhead product of a distilling column.

In redistillation systems, distilling columns are provided whose purpose is to separate the high-purity distillate from other matter such as refined hydrocarbons which are obtained in conjunction with coking, for instance. In such distilling columns, the amounts of refiux are relatively high as compared with the quantities removed as product.

For economical operation of a distilling column it is, inter ali-a, necessary that the temperature of the reflux be maintained constant throughout the process. From this follows that single-stage, air-cooled overhead condensers, particularly those which employ externally finned tubes as cooling elements, are unsuited for this purpose, since the temperature of the reflux is subject to varations that are due to the direct efiect on the air-cooled heat-exchanging surfaces of the ever varying atmospheric conditions such as air temperature, solar heat, rain, wind, and snow.

In addition, the temperature of the condensate is determined also by operational steps such as a change in the admission of heat to the condenser.

Here-tofore, basically, two-stage distilling columns have opera-ted as follows: In the first stage, an air-cooled condenser is provided in which the vapors from the distilling column are reduced to liquid. The so obtained condensate, however, will either cool down only to a temperature that is slightly lower than the condensing temperature or not at all. This so-called hot condensate is collected in a hot well. Part of the hot-well liquid is then fed in controlled quantities to a second cooling stage which comprises also an air-cooled condensate cooler that is independent of the first air-cooled condenser.

In the second condensate cooler, the hot-well liquid is cooled down to cold condensate which then flows to a mixing well. In addition to the cold condensate from the second cooling stage, the mixing well also receives hotwell liquid from the first cooling stage through an overflow in the hot Well. It should be noted here that the latter portion of hot-well liquid from the first cooling stage flows through the overflow of the hot well directly into the mixing well rather than through a valve-controlled pipe. Thus, a mixed condensate is obtained in the mixing well which consists of a predetermined amount of cold condensate and of overflow liquid from the hot well.

The temperature of the mixed condensate is sensed by a suitable heat-sensing element which through suitable switching means such as electrically actuated contacts, controls the temperature by adjusting the supply of the components of the mixture to the mixing well accordingly. That is to say, the temperature of the mixed condensate is selectively adjustable within the temperature range between the hot-well liquid from the first cooling stage and the cold condensate from the second stage.

In the past, heat-transfer devices of the type described hereinbefore have had the disadvantage that they were not suited for being mounted at the top of a distilling column because of the numerous apparatus required for controlling the cooling process. Rather conventional process condensers have to be mounted on the ground adjacent the column. With such an arrangement, however, all the advantages that are normally attained when air is used as cooling medium for an overhead condenser will be lost. Instead, such an air-cooled condenser system would be subject to the same disadvantages that are inherent in watercooled systems which serve the same purpose and which must be necessarily installed on the ground in proximity to the column. Disadvantages of such ground installations include, inter alia, the use of pumps for returning the reflux and for passing the vaporous overhead product through long pipelines of relatively large diameters.

It is accordingly a primary object of the invention to eliminate the disadvantages heretofore encountered in process condensers employing air-cooling.

It is a further object of the invention to provide a process condenser of compact construction in which two-stage air-cooling is employed.

Another object of the invention is to provide a two stage surface condenser in which the cooling elements serve the dual purpose of condensing the vaporous overhead product trom the column and cooling the condensate.

Still another object of the invention is to provide an air-cooled surface condenser for use at the top of a distilling column.

A further object of the invention is to provide an aircooled process condenser in which the etfects of the everchanging atmospheric conditions are greatly reduced.

Finally, it is an object of the invention to minimize the distance between the top of a distilling column and a condenser.

The condenser of the invention has an adjustable exhauster as well as first-stage means for condensing a vaporous overhead product or distillate and second-stage means for cooling a suitable portion of the condensate from the first stage in controlled quantities.

In accordance with one feature of the invention, an enclosed structure is provided which carries an air dome with diffuser and exhauster means. Inside the structure a vapor distribution chamber is arranged which is in communication with vapor supply pipes. Vapor lanes branch from the vapor distribution chamber, the lanes being laterally defined by cooling elements.

According to another feature of the invention, the cooling elements have fins on the air side of their cooling surfaces.

In accordance with a further feature of the invention, a number of condensate collection trays are arranged on ditferent levels in the lower section of the condenser, whereby vapor condensing zones and zones for cooling the condensate are established.

According to another feature of the invention, the condensate collection trays are slightly inclined with respect to the horizontal so that they can be used as guide elements for the condensate because of the available head.

The incorporation of the condenser components in an enclosed structure of preferably rectangular outline has the advantage of a compact arrangement which, when made statically stable, may be mounted on the top of a distilling column, even if the column 'were considerably high.

In addition, such an arrangement has the advantage that it permits the condenser to be operated properly, irrespective of prevailing atmospheric conditions. This is all the more true, since the effect of such atmospheric conditions is also undesired in condensers employing twostage cooling.

A further advantage of the invention is that only short connecting pipes are required for establishing communi- .3 cation between the head of the distilling column and the condenser, thereby avoiding pressure losses as the vaporous overhead product is fed to the condenser. Moreover, no expensive heat insulation is required.

In the condenser of the invention, the cooling elements which have fins on the air side of their cooling surfaces are used to define the condensing zones which, according to the invention, are relieved from their function as vapor distributor so that the effects of atmospheric conditions on the control of the condensing process may be neglected.

Another advantage of the arrangement of the invention is that no pumps are required. This is so, because the inclined condensate collection trays within the vapor lanes cause the condensate running down from the cooling surfaces of the cooling elements to flow back by gravity to the uppermost exchange plate of the distilling column.

In addition, the cascaded arrangement of the condensate collection trays within the vapor lanes has the advantage that part of the latent heat of the liquid is given olfto the contacted surfaces of the cooling elements as the condensate flows through the lower portion of the lanes. In this connection it is also of advantage that the condensate flows through the lanes in a zigzag course, that is, in counter-flow, transversely to the path of the cooling air.

To facilitate the control of the reflux and its temperature, the lower portion of the vapor distribution chamber is separated by dividing walls from the lanes making up the condensing section, at the same time establishing communication between the condensate storage tank and the bottom of the lanes through adjustable by-passes.

To mix cooled condensate with non-cooled condensate, a plurality of trays are arranged in the condensate storage tank in the form of a cascade. In this manner the obtained condensate can be discharged directly from the bottom of the lanes and transferred to a separate collecting pipe through the afore-mentioned by-passes, provided the valves between the by-passes and the condensate storage tank are closed.

Alternatively, it is possible, with the by-passes closed, to collect the condensate until it flows over into the storage tank. In this way, a well-cooled condensate is obtained in the storage tank. A special advantage of the cascaded tray system in the storage tank is that the trays permit any desired mixtures to be made from cooled condensate with non-cooled or less cooled condensate without any difficulty.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, as Well as additional objects and features thereof, will best be understood from the following description when considered in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a cross-sectional view of one of the internally finned cooling elements which may be employed in the present invention for instance for defining the lanes by placing the elements with their narrow surfaces side by side;

FIGURE 2 is a vertical cross-section through the condenser of the invention taken along line A-A of FIG. 4;

FIGURE 3 is a detail view of a portion of a condensate collection tray;

FIGURE 4 is a vertical cross-section through the condenser of FIG. 2 taken along the line BB' of FIG. 5;

FIGURE 5 is a horizontal cross-section through the condenser of the invention taken along line C-C of FIG. 2;

FIGURE 6 is an enlarged detail view of FIG. 5, and

FIGURE 7 is a perspective view of another embodiment of a cooling element with vapor and cooling channels.

Referring now more particularly to FIGS. 2 and 4, the vaporous overhead product from a distilling column (not shown) is fed through pipes 1 (herein designated as vapor lines) to a vapor distribution chamber 2 in an enclosed structures 3, whence it enters vapor lanes 4.

As shown in FIG. 1, lanes 4 are defined by cooling elements 5 of rectangular cross-section, inside of which are disposed fin members 5. Elements 5 extend vertically through the condenser and exit at the top into an airsupply dome 20. At their lower. ends, cooling elements 5 are open. The condensate obtained on the outer surfaces of cooling elements 5 flows down along the elements to condensate collection trays 6.

Preferably, collection trays 6 consist of sectional strips tapering in cross-section and having grooves 6 at their narrow sides for receiving correspondingly shaped sealing members 6". Trays of the type described above can be easily inserted into lanes 4 and held in place therein for instance by suitable adhesive or bonding means.

By the arrangement of condensate collection trays 6 and by further providing a system of cascaded trays 7 in conjunction with dividing walls 8 serving as separating means, the condensate will flow in a zigzag course, that is, in counter-current, transversely to the path of the cooling air, through the lower portions of lanes 4 which form the second cooling stage.

As the condensate flows through these lower lane portions, it gives off latent heat. Subsequently, the condensate flows through connecting members 9 into collecting pipes 10. The discharge of the condensate through pipes 11 is controlled by suitable valve means 12. That is to say, with the valves 12 closed, all the condensate will accumulate because of the damming effect of dividing walls 8, so that it flows off directly through vapor distribution chamber 2 to a cascaded tray system 13 in a condensate storage tank 14. However, if the valves are entirely open, all the condensate will flow through the lower cooling zone along collection trays 6 and 7 to the cascaded tray system 13. Any intermediate position of valves 12 will determine the ratio of hot condensate that flows off directly, to cold condensate from the lower or second cooling stage. In the cascaded tray system 13, a mixed condensate of a certain temperature is obtained from the hot and cold component condensates. The mixed condensate is collected in condensate storage tank 14, and its temperature is sensed by a suitable heat-sensing element (not shown) which serves to adjust the regulating valves 12 automatically through conventional relay means (not shown), depending upon the temperature sensed.

Thus the temperature of the mixed condensate is selec' tively adjustable within the temperature range between the relatively hot condensate from the condensing section and the relatively cold condensate from the cooling stage. The ratio of leaving condensate to condensate reflux is determined by regulating valve 15. A suitable portion of the condensate leaves the storage tank 14 through pipe 16,

while the remaining portion of the condensate is returned to the distilling column via overflow means 17.

Finally, to recool the noncondensable inert gases which are always present in the vapor, the gases are directed along upper trays 18 serving as guides through the upper section of lanes 4 to which the vapor is not directly admitted. From this zone the gases are then passed to channels 19 defined by trays 18 from which they can be removed by suitable means through :pipe 19, which terminates in an upper portion of vapor distribution chamber 2, the upper portion being separated from chamber 2 by a partition 18.

The vapor lanes are sealed both at the top and the bottom. The side walls of the enclosed structure 3 carry the air-supply dome 20 and the exhauster housing 21. with diffuser means 22. A gear unit 23 with impeller means 24 is mounted on the reinforced upper supporting plate of vapor distribution chamber 2. Exhauster 24 sucks the cooling air upwards through the vertically arranged, internally finned cooling-air elements 5.

According to another embodiment shown in FIG. 7, the cooling-air elements may consists of properly dimensioned plate sections 25 each of which has fins on its one side. For assembly, the finned plate sections are liquidand vapor-tight connected in pairs in such a manner that a space 29 is formed by the nonfinned surfaces of each pair of plate sections. Thus, unlike the embodiment of FIG. 1, the pairs of finned plate sections of FIG. 7 act as vapor guide elements which, when assembled, will define finned air channels 30.

The arrangement shown in FIG. 7 has the advantage that the elements employed may be more easily fabricated. Preferably, the plates are first formed to the desired shape, with their connecting edges 26 offset and with spacing projections 27 formed across their nonfinned surfaces.

FIG. 7 is a detail view of a portion of a condenser employing cooling elements of the type just described. For sake of simplicity, only the left-hand and central channels are shown provided with fins 28. The projections 27 serve the purpose of preventing the sheets from being compressed or bent together under the force of the air pressure.

It sohuld be understood that the air channels 30 would be laterally closed by walls 31. For sake of clarity, wall 31 of the left-hand channel 30 has been omitted. The dashed arrows indicate the direction of vapor flow, whereas the solid arrows indicate the direction of air flow.

With the ambient temperature given, the eificiency of the heat transfer surface is determined solely by the quantity of air delivered by the exhauster or by the velocity of the air in the channels.

In the foregoing, a specific embodiment of the invention has been described, but it should be understood that modifications and changes may be made without departing from the spirit and scope thereof.

What is claimed is:

1. A distillation column having a condenser for arrangement at the top of the distillation column, the said condenser comprising air-conducting elements which are disposed in a containing vessel, said vessel being secured by mounting elements to the upper end of said distilling column, vapor pipe means which are arranged between said distilling column and said containing vessel to establish communication between said column and said vessel, a vapor distribution chamber which is centrally disposed in said containing vessel, said vapor pipe means exiting into said vapor distribution chamber, said air-conducting elements containing fin members and establishing vertical channels which exit at their upper ends into an air-conducting dome, said air-conducting elements being spaced within the vessel to horizontal channels therebetween which communicate with said vapor distribution chamber, condensate collection tray means arranged at the bottom of the vessel having said horizontal channels for cascade of condensate and communicating with a condensate discharge means and a condensate to storage tank, gas olftake means at the top of the vapor distribution chamber, fan means being disposed in said air-conducting dome, overlying the vessel, said condensate storage tank being arranged beneath said vapor distribution chamber and being in communication through valve means containing condensate pipe means with condensate passages defined by said condensate collection tray means, overflow means disposed in said condensate storage tank and leading to said distillation column, and a condensate discharge pipe which is in communication with said condensate storage tank.

2'. The condenser as set forth in claim 1 wherein said condensate collection tray means are arranged in the form of cascades to provide cross-flow of the condensate with respect to the air-flow.

3. The condenser as set forth in claim 1 wherein baflie plates are disposed in said vapor distribution chamber adjacent to said condensate collection tray means.

4. The condenser as set forth in claim 1 wherein a plurality of cascaded directing elements are disposed in said condensate storage tank to mix hot condensate with cold condensate.

5. The condenser as set forth in claim 4 wherein said condensate pipe means exit into said condensate storage tank in proximity to said plurality of cascaded directing elements.

6. The condenser as set forth in claim 4 wherein said condensate storage tank is in open communication with said vapor distribution chamber.

7. The condenser as claimed in claim 1, wherein said fan means are of the exhauster type.

8. The condenser as set forth in claim 1 wherein said gas oiftake means comprise gas-conducting elements, an otftake chamber and at least one oiftake pipe exiting into said offtake chamber, said gas-conducting elements being disposed in the upper section of the vapor channels of said takeoff chamber.

9. The condenser as set forth in claim 1 wherein the air-conducting elements are composed of hollow, internally finned, elongated members of substantially rectangular cross-section.

10. The condenser as set forth in claim 1 wherein the air channels are defined by pairs of plate sections, the sections of each pair being airand vapor-tight connected to each other and being provided with spacing projections on their nonfinned surfaces and with fins on their air side, each pair of plate sections enclosing a vapor lane.

References Cited UNITED STATES PATENTS 3,165,455 1/1965 Rose et al. 202189 3,236,746 2/ 1966 Poindexter et al. 202206 X FOREIGN PATENTS 921,492 3 1963 Great Britain. 927,918 6/ 1963 Great Britain.

NORMAN YUDKOFF, Primary Examiner.

F. E. DRUMMOND, Assistant Examiner. 

1. A DISTILLATION COLUMN HAVING A CONDENSER FOR ARRANGEMENT AT THE TOP OF THE DISTALLATION COLUMN, THE SAID CONDENSER COMPRISING AIR-CONDUCTING ELEMENTS WHICH ARE DISPOSED IN A CONTAINING VESSEL, SAID VESSEL BEING SECURED BY MOUNTING ELEMENTS TO THE UPPER END OF SAID DISTILLING COLUMN, VAPOR PIPE MEANS WHICH ARE ARRANGED BETWEEN SAID DISTILLING COLUMN AND SAID CONTAINING VESSEL TO ESTABLISH COMMUNICATION BETWEEN SAID COLUMN AND SAID VESSEL, A VAPOR DISTRIBUTION CHAMBER WHICH IS CENTRALLY DISPOSED IN SAID CONTAINING VESSEL, SAID VAPOR PIPE MEANS EXITING INTO SAID VAPOR DISTRIBUTION CHAMBER, SAID AIR-CONDUCTING ELEMENTS CONTAINING FIN MEMBERS AND ESTABLISHING VERTICAL CHANNELS WHICH EXIT AT THEIR UPPER ENDS INTO AN AIR-CONDUCTING DOME, SAID AIR-CONDUCTING ELEMENTS BEING SPACED WITHIN THE VESSEL TO HORIZONTAL CHANNELS THEREBETWEEN WHICH COMMUNICATE WITH SAID VAPOR DISTRIBUTION CHAMBER, CONDENSATE COLLECTION TRAY MEANS ARRANGED AT THE BOTTOM OF THE VESSEL HAVING SAID HORIZONTAL CHANNELS FOR CASCADE OF CONDENSATE AND COMMUNICATING WITH A CONDENSATE DISCHARGE MEANS AND A CONDENSATE TO STORAGE TANK, GAS OFFTAKE MEANS AT THE TOP OF THE VAPOR DISTRIBUTION CHAMBER, FAN MEANS BEING DISPOSED IN SAID AIR-CONDUCTING DOME, OVERLYING THE VESSEL, SAID CONDENSATE STORAGE TANK BEING ARRANGED BENEATH SAID VAPOR DISTRIBUTION CHAMBER AND BEING IN COMMUNICATION THROUGH VALUE MEANS CONTAINING CONDENSATE PIPE MEANS WITH CONDENSATE PASSAGES DEFINED BY SAID CONDENSATE COLLECTION TRAY MEANS, OVERFLOW MEANS DISPOSED IN SAID CONDENSATE STORAGE TANK AND LEADING TO SAID DISTILLATION COLUMN, AND A CONDENSATE DISCHARGE PIPE WHICH IS IN COMMUNICATION WITH SAID CONDENSATE STORAGE TANK. 